Epigenetic regulation has crucial implications for myocardial fibrosis. It has been reported that autophagy, regulated by miR-145, is implicated in the proliferation and fibrosis of cardiac fibroblasts (CFs). However, how it works during the process remains unclear. This study explored the exact effects of epigenetic regulation of miR-145 expression on autophagy, proliferation, and fibrosis of CFs. To examine the expression levels of myocardial fibrosis markers (α-SMA and collagen I), autophagy-related proteins (LC3I, LC3II, p62), DNMT3A, and miR-145, qRT-PCR and western blot were employed. And the proliferation of CFs was detected by CCK-8 and ErdU. As for the determination of the binding relationship between DNMT3A and miR-145, dual-luciferase assay was conducted. Next, the detection of the methylation level of the pre-miR-145 promoter region was completed by MSP. And the verification of the effect of the DNMT3A/miR-145 axis on myocardial fibrosis was accomplished by constructing mouse myocardial infarction (MI) models based on the ligation of the left anterior descending method. In TGF-β1-activated CFs, remarkable up-regulation of DNMT3 and considerable down-regulation of miR-145 were observed. And further experiments indicated that DNMT3A was able to down-regulate miR-145 expression by maintaining the hypermethylation level of the pre-miR-145 promoter region. In addition, DNMT3A expression could be directly targeted and negatively modulated by miR-145. Moreover, in vitro cell experiments and mouse MI models demonstrated that DNMT3A overexpression could inhibit autophagy, and promote cell proliferation and fibrosis of CFs. However, this kind of effect could be reversed by miR-145 overexpression. In summary, myocardial fibroblast autophagy can be regulated by bidirectional negative feedback actions of DNMT3A and miR-145, thus affecting myocardial fibrosis. This finding will provide a potential target for the clinical treatment of myocardial fibrosis.

表观遗传调控对心肌纤维化具有重要意义。据报道，受 miR-145 调节的自噬与心脏成纤维细胞 (CF) 的增殖和纤维化有关。然而，其在此过程中如何运作仍不清楚。本研究探讨了 miR-145 表达的表观遗传调控对 CFs 自噬、增殖和纤维化的确切影响。为了检测心肌纤维化标志物（α-SMA 和胶原蛋白 I）、自噬相关蛋白（LC3I、LC3II、p62）、DNMT3A 和 miR-145、qRT-PCR 和蛋白质印迹的表达水平。CCK-8和ErdU检测CFs增殖情况。为了确定DNMT3A和miR-145之间的结合关系，进行了双荧光素酶测定。接下来，通过MSP完成pre-miR-145启动子区甲基化水平的检测。并通过左前降支结扎法构建小鼠心肌梗死(MI)模型来验证DNMT3A/miR-145轴对心肌纤维化的影响。在 TGF-β1 激活的 CF 中，观察到 DNMT3 显着上调，而 miR-145 显着下调。进一步的实验表明，DNMT3A能够通过维持前miR-145启动子区域的高甲基化水平来下调miR-145的表达。此外，DNMT3A 表达可以直接被 miR-145 靶向和负向调节。此外，体外细胞实验和小鼠MI模型表明，DNMT3A过表达可以抑制自噬，促进CFs细胞增殖和纤维化。然而，这种效应可以通过 miR-145 过表达来逆转。综上所述，心肌成纤维细胞自噬可以通过DNMT3A和miR-145的双向负反馈作用进行调节，从而影响心肌纤维化。这一发现将为心肌纤维化的临床治疗提供潜在靶点。